This relates in general to poles and associated attachments constructed to support electrical current-bearing utility cables, namely, telephone poles, electrical power poles, light poles, and the like, and more particularly to such poles which are preformed of insulating material such as a fiber-resin composite, such as glass fiber reinforced resin, and the like, and the fabrication of the same.
In our present power-hungry industrialized society, it is necessary that cables carrying high voltage electrical currents criss-cross the land. In accordance with present practice, most of these cables are supported on wooden or metal poles or supporting structures which have a number of disadvantages.
Wooden poles are subject to normal deterioration, such as rotting, and are also subject to attack by insects, such as termites, and woodpeckers and other birds. Furthermore, because wood is a carbon-based organic material, such wooden poles, especially when water soaked, are highly susceptible to disruptive lightening strikes. This poses a safety hazard to the linesmen working on the transmission amd distribution systems, and also to casual bystanders.
Furthermore, metal poles are substantially more expensive and also poses a safety hazard unless provided with highly insulating attachments.
Poles of plastic, or glass fiber reinforced resin, have been known in the prior art; but their manufacture, according to prior practice, has been cumbersome and expensive. For example, in accordance with one process, plastic poles are constructed in sections, as disclosed in U.S. Pat. No. 2,841,634, issued on July 1, 1958 to Clarence L. Kimball. Another type of plastic pole is constructed in the form of tubular sheaths disposed longitudinally and impregnated with a thermosetting resin, and comprises a tubular liner sleeve made up of a plurality of radially-disposed circumferential strips also impregnated with thermosetting resin. This type is disclosed in U.S. Pat. No. 3,013,584, issued Dec. 19, 1961 to Clair S. Reed and William Russell Bailey. Another form of pole, consisting essentially of glass fiber reinforced resin, is constructed in the form of a longitudinally-extending tapered column, formed by intermittently pressing and rolling resin and glass fibers on a mandrel comprising a frame having radially-extending fins, as disclosed in U.S. Pat. No. 3,813,837, issued to Stephen A. McClain, Harvey A. Doman, and Richard D. Entus on June 4, 1974.
It is the primary object of this invention to provide an improved design of a utility pole of glass fiber reinforced resin, and the like, which is less expensive and simpler to fabricate than those of the prior art. Another object of the invention is to provide an improved method for fabricating utility poles of glass fiber reinforced resin, and the like. Other objects of the invention are to increase the safety and dependability of utility systems employing poles designed in accordance with the present invention.
These and other objects of the invention are realized in a one piece, hollow, reinforced utility pole of glass fiber reinforced resin, or the like, manufactured by a process called `pultrusion`. This is defined as a process for producing reinforced plastic profiles in continuous lengths by pulling raw materials, comprising thermosetting resins and fiber reinforcements, through uniquely pre-shaped dies in a series of operations in which they are progressively combined, shaped and cured. The product of this process is a hollow tubular structure having internal diametrical reinforcing struts which terminate externally in laterally-projecting fins which extend the length of the tube.
The fins are adapted to accommodate elongated cable-bearing connectors having longitudinal slots, which are adapted to seat onto and be bolted into place on perforations in the fins. Each of the connectors has a plurality of laterally-extending slots which are constructed to close against and support a horizontally-extending array of utility cables. In one embodiment, the connectors are bolted into place against the utility cables with the pole in its upright position; and in another embodiment, the connectors are bolted into place initially, before the pole is raised, and an elongated plug is dropped vertically into position to secure the horizontal array of utility cables in place in the lateral slots.
For protective purposes, to keep water and animals out of the interior, a frusto-pyramidal cap is superposed over the top of the hollow pole; and an anti-roost attachment may be mounted on the top to prevent birds and other animals from roosting there.
A clearance of 1/2 inch between the pole and the cap and the elliptical holes eight feet above ground level permit natural convection to ventilate the four internal conduits.
A utility pole constructed in accordance with the present invention has the advantage of being formed in one piece to any desired length, and of a uniform cross-section. It is completely insulating, and resistant to animal and insect damage and natural deterioration, such as rotting. A most important feature of the utility pole design of the present invention is the safety which it affords to the linesmen, enabling them to secure the utility wires in place simply, and with a minimum hazard of possible short circuits. Furthermore, the insulating character, strength, and resilience of the poles of the present design make them safe against strikes by lightening and wind damage, thus preventing wide spread utility failure due to storms, and thus saving millions of dollars to utility companies and their customers.
Utility patents in accordance with the present invention are deemed to provide the following additional advantages over wooden utility poles:
a. Glass fiber poles weigh an average 25% of the weight of wooden poles. e.g. (50 ft. wooden pole weighs 2,000 pounds; a glass fiber pole weighs 500 pounds).
b. They require lower labor, handling and shipping costs.
c. Cross arms are eliminated, saving the cost of the arms, metal support components, installation labor and insulators.
d. The attachment assembly of the present invention firmly secures conductors so they cannot loosen and fall to the ground.
e. There are no ceramic insulators, removing temptation as targets for hunters.
f. The material of the poles of the present invention are chemically resistant to acid soil.
g. They will not absorb moisture from ground water, rain or snow.
h. They are environmentally safe, and will not contaminate underground water tables.
i. They are resistant to attack by termites and other insects.
j. The smooth surface of the material employed prevents woodpeckers from getting a foothold, and prevents squirrels from climbing these poles.
k. The poles and assemblies of the present invention are resistant to urine deposited by male dogs and uric acid from birds.
l. They are resistant to the heat and cold of the elements.
m. They include four internal conduits for electric and phone lines.
n. They are designed so conduits are ventilated by natural convection.
o. The material is formulated for high dielectric strength, arc and track resistance, flame retardance and ultra-violet radiation inhibitor.
p. The unique design of the present invention minimizes movement or twisting once the pole is implated in the ground.
q. Glass fiber poles in accordance with the present invention can be cut to desired length, with no waste.
r. Depending on shipping restrictions, a single piece can be of unlimited length.
s. For higher visibility at night, color could be added to the poles, or their accessories.
t. A pole top cover (extra cost), compression molded of glass fiber provides additional cable-bearing assembly and anti-roost design, discouraging birds, squirrels and other animals.
u. Millions of miles of copper wire used in lightening protection for prior art systems would be sharply reduced.
v. High dielectric properties of the material, arc and track resistance tend to reduce creepage distance between current carrying conductors to inches instead of feet.
w. The reduced creepage distance tends to reduce the required height for poles and, in turn, to reduce the cost of a higher pole.
x. The need for circuit breakers used on distribution lines will be reduced.
y. The high dielectric properties of the material give the poles of the present invention insulation values so lightening is not attracted, thereby rendering them immune to lightening strikes.
z. The surface hardness of the material should reduce the use of poles in accordance with the present invention for tacking up political signs, yard sales, clothes lines, etc.
aa. A hurricane or tornado builds up high pressure against the cross arms on wooden poles, the most likely cause for wood poles snapping at the base. There are no cross arms on poles designed in accordance with the present invention.
These and other objects, features, and advantages will be apparent from a detailed study of the specification hereinafter with reference to the attached drawings.